Small molecule found, boosts mouse memory

By Erin Allday, Victoria Colliver |
June 18, 2013

SMALL MOLECULES

New chemical found, aids mouse memory

Mice injected with a newly identified chemical improved their performance on several simple memory tests, a finding that could help scientists better understand a host of human memory disorders associated with brain diseases and aging, according to researchers at UCSF.

Scientists found the molecule after screening 100,000 chemicals at UCSF's Small Molecule Discovery Center. The molecule, called integrated stress response inhibitor (ISRIB), is able to counteract the effects of a protein that may halt memory formation when cells are under stress.

When the protein is activated, it beefs up production of other proteins that help cells cope with stressors like DNA damage or viral infections. But at the same time, activation of that protein shuts down other proteins that are thought to be involved with building memories.

The ISRIB chemical appears to interfere with the process of shutting down memory-building proteins.

Mice given the chemical were three times faster at locating a submerged platform than mice that received a placebo. They also were better at recalling cues associated with negative stimuli.

The chemical is not ready to be tested in humans. Instead, scientists hope to use it to improve their understanding of diseases that affect the memory, as well as biological reactions to stress.

METABOLISM

Protein linked to circadian clock

Scientists at the Gladstone Institutes have found evidence that a protein known to play an important role in several metabolic processes seems to ebb and flow in time with the body's circadian clock.

When the scientists disrupted the clock of mice by removing a gene known to help control the circadian rhythm, they found that production of the protein, called p75 neurotrophin receptor, waned. The drop in protein production seemed to disrupt circadian genes in the brain and liver, plus genes that help regulate glucose and fat metabolism.

All of those effects suggest that the protein is not only closely tied to the body's circadian clock, but that removing the protein further disrupts the clock and important metabolic processes.

Scientists believe the discovery could improve research into the complex biological processes that make up the circadian clock. And it adds more proof to the idea that the circadian clock plays an important role in maintaining a healthy metabolism.

A paper on their research was published Tuesday in the Journal of Neuroscience.

- Erin Allday

HEARING

Brain doesn't sweat small stuff

When the human brain is faced with making sense of complex sounds, it focuses on the big picture instead of the little details, new UC Berkeley research shows.

In the study, nearly two dozen participants overall could judge the average pitch of a brief sequence of tones. But they had trouble recalling information about individual tones within the sequence.

The authors said their results suggest that the brain automatically summarizes sounds, such as music, to get a gist of what is being heard, instead of processing individual notes. The findings could be used to, for example, improve hearing aids so that hearing-impaired people can tune into one conversation while multiple conversations are going on in the background.

The study was published last week in the journal Psychological Science.

AUTISM

Brain wiring and communication gaps

Autistic children often struggle to grasp the social and emotional aspects of human speech, and a new study from the Stanford University School of Medicine illuminates a brain mechanism that could explain why.

In autistic youth, brain regions tailored to respond to voices are poorly connected to reward-processing circuits that normally allow children to experience speech as pleasurable, the authors said.

The study involved 20 children with a high-functioning form of autism: they could speak and read but had difficulty understanding emotional cues in another person's voice. The scientists compared MRI brain scans from these children with scans from 19 typically developing children.

They found that in the autistic group, the voice-selective cortex on the left side of the brain was weakly connected to brain structures that release dopamine in response to rewards: the nucleus accumbens and the ventral tegmental area. And the voice-selective cortex on the right side of the brain, which specializes in detecting vocal cues such as intonation and pitch, was weakly connected to the amygdala, which processes emotional cues.

The weaker these connections in autistic children, the worse their communication gaps, the study found. Scientists say their findings could help develop new treatments for autism.

COMPUTED TOMOGRAPHY

Fewer, weaker scans may cut kids' cancer risk

Reducing the number of unnecessary CT scans for children and lowering the doses for the highest-dose scans could cut the lifetime risk of imaging-related cancers by as much as 62 percent, UC Davis researchers have found.

Radiation doses delivered by CT, or computed tomography, are 100 to 500 times greater than conventional X-rays and are associated with increased cancer risk.

The researchers estimated 4,870 future cancers could be caused by the approximately 4 million CT scans performed on children each year. They found that just by reducing the amount of radiation in the highest 25 percent of the CT scans in children, about 43 percent of future cancers could be prevented.

CT use increased from 1996 to 2005, doubling for children younger than 5 and tripling for children between ages 5 and 14 during that time period. That percentage started decreasing after 2007, possibly because of concerns about radiation exposure.

Researchers conducted the study by examining nearly 750 CT scans of the head, abdomen/pelvis, chest and spine conducted on children under the age of 15 between 2001 and 2011.